HVAC systems can include premix burners, furnaces, and other components that combust a mix of fuel and air. Fuel is often provided by a utility hookup. Air is provided in such applications by an air inlet that usually pulls air from the atmosphere. Because air is drawn from the atmosphere, there is a risk of foreign matter being drawn into the air intake, the gas-air mixer, the premix burner, furnace heat exchanger or another component. Foreign matter such as dust, leaves, bugs or other things can be detrimental, causing mechanical failure or suboptimal operation.